Power saving mechanisms in wireless communication systems can specify periods of time during which a wireless device enters a lower power state, such as an idle or sleep state, in which a transceiver or radio is powered down to conserve power. After each specified period of time the radio can be powered up for a brief wake duration (such as one MAC frame) to determine whether data is pending delivery to the wireless device. If no data is pending delivery, the wireless device is returned to the low power state. On the other hand, if data is pending, the wireless device is transitioned to a higher power (fully awake) state in which the radio is powered on to receive the data, and delivery of the data can be scheduled thereafter. Depending on when the data arrives for delivery to the wireless device, the timing of the sleep state can delay the delivery of the arrived data. For example, if the data arrives at the beginning of the wireless device's sleep state period, delivery of the data will be delayed until the sleep state period ends and the wireless device enters the brief wake duration.